Starspots are regions on the surface of a star that are cooler than their surroundings. Temperature affects brightness, so starspots can significantly alter the overall appearance of a star even when individual starspots can’t be distinguished. But if we characterize starspots in detail, we should be able to account for their effects.
The constellation Andromeda from Uranographia by Johannes Hevelius. λ Andromedae is just to the left of Andromeda’s thumb on her outstretched arm. [Torsten Bronger]
Old and New Ways of Finding Starspots
Starspots are thought to be caused by stellar magnetic activity, so as much as they can obscure true stellar properties, they can also help us learn about the interiors of stars. We’ve also noticed that our Sun’s starspots behave very differently than starspots on other stars, adding another motivation to examine these phenomena on other stars.
Until recently, starspots have been studied through indirect methods like light curve modeling and Doppler imaging, which measures changes in stellar spectra caused by magnetic fields. These techniques have broadened our understanding of starspots, but they are also hamstrung by requiring certain assumptions about the stars being observed.
Direct imaging of starspots has been made possible through a relatively new ...